Mole Fraction
 The mole fraction is a unit of concentration, defined to be equal to the number of moles of a component divided by the total number of moles of a solution
 The mole fraction is determined for all reactants in a mixture of gases
 g. to find the mole fraction of A (X_{a}):
Partial pressure
 Partial pressure it the pressure exerted by the single gas if it were isolated
 The total pressure is the combined total of all the partial pressures
 To determine the partial pressure for one gas, multiply the mole fraction by the total pressure
 g. to find the partial pressure of A (P_{A}):
 Units for partial pressure Pascals or atmospheres
P_{A} = Mole Fraction of A x Total Pressure
P_{A} = X_{a} x P
K_{p} in homogeneous gaseous equilibria

 Homogeneous Equilibria refers to all involved reactants are in the same phase
 For Kp to function, everything must be a gas
 Kp will always be a constant except for a change in temperature
K_{p} in heterogeneous equilibria
 Heterogeneous equilibrium will involve gases in contact with solids
 As Kp functions only with a gas, the solid is not included